What to Do in a Gas Leak Emergency

Gas leaks are rare but they do happen — and the first few minutes matter enormously. As a Gas Safe registered engineer in the West Midlands I attend a number of gas leak call-outs every year, and the customers who handle them best are always the ones who already knew what to do. This guide gives you that knowledge now, before you ever need it.

What Does a Gas Leak Smell Like?

Natural gas itself is actually odourless. Gas suppliers deliberately add a chemical called mercaptan (ethyl mercaptan) to give it a distinctive, unmistakable smell. Most people describe it as rotten eggs, sulphur, or a heavy, pungent chemical odour.

If you can smell this — even faintly — treat it as a gas leak immediately. Do not wait to see if the smell gets stronger, and do not try to track down the source yourself.

Other signs of a possible gas leak include: a hissing or whistling sound near a gas appliance or pipe, dead or discoloured vegetation near an outdoor gas pipe, or an unexplained increase in your gas bill (which can indicate a slow leak in the system).

What to Do — Step by Step

What NOT to Do

These are the most common mistakes people make during a gas leak — any of them can turn a manageable situation into a disaster:

• Do not turn any electrical switches on or off — this includes light switches, fans, extractor fans, and appliances
• Do not use your mobile phone, doorbell, or any electrical device inside the building
• Do not try to find the source of the leak yourself
• Do not attempt to repair the leak yourself — even turning a gas appliance off at the appliance itself can cause a spark
• Do not re-enter the building until the emergency engineer has confirmed it is safe
• Do not turn the gas back on yourself after a leak — the system must be inspected and cleared by a Gas Safe registered engineer first

After the Emergency Service Have Been

The National Gas Emergency Service will make the situation safe — but their job is emergency containment, not repair. After they have attended and declared the property safe, you will typically need:

• A gas leak detection inspection to identify exactly where the leak occurred
• Repair or replacement of the faulty component (pipework, valve, appliance connection)
• A safety check of all gas appliances before the gas supply is restored
• Possibly a new gas safety certificate if the appliances have been condemned or if you are a landlord

All of this work must be carried out by a Gas Safe registered engineer. Do not let anyone touch your gas system after a leak without checking their Gas Safe card first.

Common Causes of Domestic Gas Leaks

In my experience, the most common causes of gas leaks in homes are:

• Poorly fitted appliance connections — work carried out by an unregistered person is the leading cause
• Perished or corroded pipework — especially in older properties with steel or iron gas pipes
• Faulty appliance seals — gas cookers and fires are the most common culprits
• Disturbed pipework — drilling through a wall or floor and hitting a gas pipe
• Flexible gas connectors behind cookers that have cracked, kinked, or perished over time

Many of these are preventable with regular servicing and by always using a Gas Safe registered engineer for any gas work. An annual boiler service includes a visual inspection of visible pipework and connections, which can catch deterioration before it becomes a leak.

Carbon Monoxide — the Silent Danger

Carbon monoxide (CO) is a separate but related hazard. Unlike a gas leak, you cannot smell CO — it is completely colourless and odourless. It is produced when gas appliances burn incorrectly due to a fault or poor ventilation. Every home with gas appliances should have a working CO alarm, fitted according to the manufacturer's instructions.

If your CO alarm sounds, treat it with the same urgency as a gas leak: leave the building immediately and call 0800 111 999. Read our guide on carbon monoxide symptoms to understand what CO poisoning looks like.

Frequently Asked Questions